Dynamics of microbial planktonic food web componen

Authors: David Pecqueur Francesca Vidussi Eric Fouilland Emilie Le Floc’h Sebastien Mas Cecile Roques Christian Salles MarieGeorge Tournoud Behzad Mostajir

Publish Date: 2011/05/15

Volume: 673, Issue: 1, Pages: 13-27

PDF Link

Abstract

Episodic river flash floods characteristic of Mediterranean climates are suspected to greatly affect the functioning of microbial food webs For the first time the abundance biomass and diversities of microbial food web components were studied before and during 4 consecutive days after a flash flood that occurred in November 2008 in the surface waters of five stations along a salinity gradient from 20 to 36 in the Thau lagoon Eukaryotic pico and nanophytoplankton were discharged from the river into the lagoon and increased by 30 and 70fold respectively Bacteria increased by only 2fold in the lagoon from around 4–8 × 106 cells ml−1 probably benefiting from river nutrient input Chlorophyll a increased 4fold and pigment biomarkers showed that the dinophyceae prasinophyceae and prymnesiophyceae were sensitive to the flood perturbation whereas the bacillariophyceae cryptophyceae and chlorophyceae were resistant and/or transported to the lagoon from the river Predator responses were more complex as total heterotrophic flagellate abundance decreased slightly whereas those of specific naked ciliates increased particularly for Uronema sp The flood also induced a specific change in diversity from a community dominated by Strobilidium spiralis to a community dominated by Uronema sp The tintinnid community was particularly sensitive to the flood event as the abundance of all species decreased greatly The high increases in biomass mainly brought by the river during the flood could have eventually sedimented to the benthic layer and/or been transported further into the lagoon supporting the pelagic food web or have even been exported to the Mediterranean SeaWe thank Captain Michel Cantou for field assistance Jean Nouguier for the continuous monitoring technical development Aurore Trottet for help in sampling and Romain Pete for help with statistical analyses David Pecqueur was supported by a national scientific PhD fellowship provided by the French Ministry of Education and Research This study is part of the project ‘Impact des eaux de crue sur le réseau microbien de la lagune de Thau RESTHAU’ funded by the ‘ECosphère Continentale et Côtière’ EC2CO French National Program

Keywords: